Oil leakage preventing structure of injection molding machine

The utility model relates to an oil leakage preventing structure of an injection molding machine, which is arranged in a preplastification seat. The oil leakage preventing structure of the injection molding machine comprises an injection cylinder and a piston assembly which is sealed in the injection cylinder and drives an injection screw rod to perform reciprocating and rotating motion, wherein the piston assembly comprises an injection piston as well as a preplastification piston and a preplastification piston rod which penetrate through the piston channel, rotate and synchronously reciprocate with the injection piston; a piston channel is arranged in the injection piston in the axial direction of an injection piston shaft, and the injection piston is sealed and arranged in the injection cylinder; the preplastification piston is arranged between the injection piston and the preplastification piston rod in a sleeved manner and fixedly connected with the preplastification piston rod; the front end of the prep